Linphone config on nixos

How is it possible to set

[sound]
echocancellation=1
ec_delay=100

the nix way.

That’s a config file. The runtime configs aren’t usually configured in nixpkgs. If you want you can patch the default config with another patch in the derivation or if you want something to manage your home directory/configs there’s GitHub - nix-community/home-manager: Manage a user environment using Nix [maintainer=@rycee]